SEA-FISHERIES LABORATORY. 239 



actual observations for this period of the year, it is 

 probable that temperatures of 17° to 18° characterise the 

 water in Tremadoc Bay. Round the North Coast of 

 Anglesey the temperature is very little higher than that in 

 the fairway of the Channel, because the water of this part 

 of the coast is deep, and affected to a relatively slight 

 extent by the land, and also because of the continuous flow 

 round the promontory of Anglesey. It will be seen that a 

 large part of the Irish Sea South and West of the Isle of 

 Man is now filled with water which varies in temperature 

 from 12*5° to about 13°, and inside this is a smaller area, 

 the temperature of which appears to be a little greater. 

 This warm " island " of water is established, no doubt, 

 because of the general deficiency of circulation in this part 

 of our area. In all the former charts this relatively 

 stagnant area was situated nearer to the Isle of Man, but 

 in August, when the strength of the Gulf Stream Drift is 

 nearly at its minimum value, the part of the Channel 

 covered by non-circulating water has increased greatly 

 in area. It should also be noticed that in these months, 

 when the Gulf Stream flow is weakest, the curving-in of 

 the isotherms towards Liverpool Bay occurs closer to the 

 Isle of Man than the Anglesey coast. When the flow is 

 strongest the water tends to pass closely round Anglesey. 

 Then, just as at the time of minimum temperature, the 

 isotherms in the eastern part of the Irish Sea run 

 approximately parallel to the coast line. 



September 15th, 1909. 



The observations at this time related to an inter- 

 mediate cruise, and only the eastern side of the Irish Sea 

 was investigated. The temperatures are again very 

 uniform, the greatest difference being only 1*65° The 

 Q 



